The present disclosure relates generally to systems for dispensing hot melt adhesive. More particularly, the present disclosure relates to service seats for dispense modules having valves from which melted hot melt adhesive is applied.
Hot melt dispensing systems are typically used in manufacturing assembly lines to automatically disperse an adhesive used in the construction of packaging materials such as boxes, cartons and the like. Hot melt dispensing systems conventionally comprise a material tank, heating elements, a pump and a dispenser. Solid polymer pellets are melted in the tank using a heating element before being supplied to the dispenser by the pump. Because the melted pellets will re-solidify into solid form if permitted to cool, the melted pellets must be maintained at temperature from the tank to the dispenser. This typically requires placement of heating elements in the tank, the pump and the dispenser, as well as heating any tubing or hoses that connect those components. Furthermore, conventional hot melt dispensing systems typically utilize tanks having large volumes so that extended periods of dispensing can occur after the pellets contained therein are melted. However, the large volume of pellets within the tank requires a lengthy period of time to completely melt, which increases start-up times for the system. For example, a typical tank includes a plurality of heating elements lining the walls of a rectangular, gravity-fed tank such that melted pellets along the walls prevents the heating elements from efficiently melting pellets in the center of the container. The extended time required to melt the pellets in these tanks increases the likelihood of “charring” or darkening of the adhesive due to prolonged heat exposure.
A service seat provides a secondary means for closing the valve within the dispense module when the primary, dispensing valve seat is removed. For example, the dispensing valve seat may be removed to perform maintenance, such as to clean debris or char from a dispense orifice within the dispensing valve seat. Conventional dispense modules have service seats that are configured to engage a transition section of the valve stem that is used to actuate the dispense module. One such dispense module is disclosed in U.S. Pat. No. 5,873,528 to Lewis et al. However, configuring the valve stem to engage the service seat requires additional machining of the valve stem, which adds to the expense of the valve stem.